#include<stdio.h>
main()
{	   	  	  		 
    int i = 2;//1
    int j = 0;//1
    int day = 0;//1
    float k = 0;//1
    while (i <= 100) //2
    {	   	  	  		 
        j = j + i;//1
        day = day + 1;//1
        i = i * 2; //1
    }
    k = j / day * 0.8; //2
    printf("%.2f\n", k); //2
}